test: hugepages: use SSHConnection.check_output instead of run

Seems like it got missed during the big refactor that introduced
`check_output` somehow.

Fixes: acbef3c
Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

tests/integration_tests/performance/test_huge_pages.py

@@ -128,8 +128,7 @@ def test_hugetlbfs_diff_snapshot(microvm_factory, uvm_plain, uffd_handler_paths)
     uvm_plain.resume()
 
     # Run command to dirty some pages
-    rc, _, _ = uvm_plain.ssh.run("sync")
-    assert not rc
+    uvm_plain.ssh.check_output("sync")
 
     snapshot_diff = uvm_plain.snapshot_diff()
     snapshot_merged = snapshot_diff.rebase_snapshot(base_snapshot)
@@ -181,13 +180,11 @@ def test_ept_violation_count(
 
     # Wait for microvm to boot. Then spawn fast_page_fault_helper to setup an environment where we can trigger
     # a lot of fast_page_faults after restoring the snapshot.
-    rc, _, _ = vm.ssh.run(
+    vm.ssh.check_output(
         "nohup /usr/local/bin/fast_page_fault_helper >/dev/null 2>&1 </dev/null &"
     )
-    assert not rc
 
-    rc, pid, _ = vm.ssh.run("pidof fast_page_fault_helper")
-    assert not rc
+    _, pid, _ = vm.ssh.check_output("pidof fast_page_fault_helper")
 
     # Give the helper time to initialize
     time.sleep(5)
@@ -211,8 +208,7 @@ def test_ept_violation_count(
         vm.restore_from_snapshot(snapshot, resume=True, uffd_path=SOCKET_PATH)
 
         # Verify if guest can run commands, and also wake up the fast page fault helper to trigger page faults.
-        rc, _, _ = vm.ssh.run(f"kill -s {signal.SIGUSR1} {pid}")
-        assert not rc
+        vm.ssh.check_output(f"kill -s {signal.SIGUSR1} {pid}")
 
         # Give the helper time to touch all its pages
         time.sleep(5)